JP2013161811A - Method and apparatus for cleaning substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for cleaning a substrate, the apparatus preventing substrates from sticking to each other without reducing productivity.SOLUTION: The apparatus for cleaning a substrate includes: a cleaning tank 105 storing a cleaning fluid 104; a carrier cassette 102 for holding and accommodating a plurality of substrates 101 being arranged so as to be spaced from each other at a predetermined interval; a carrier transfer machine 103 for taking the carrier cassette 102 in and out of the cleaning tank 105; and bubble supply means (a bubble introduction recess 106 and a bubble generating feeder 107) for mixing bubbles into the cleaning fluid between the substrates 101 in the carrier cassette 102 immersed in the cleaning tank 105. The apparatus controls to immerse the substrates 101 in the cleaning fluid 104 to clean them, mix bubbles into the cleaning fluid between the substrates 101, and raise the carrier cassette 102 from the cleaning tank 105 to take out the substrates 101 from the cleaning fluid 104 while the cleaning fluid mixed with the bubbles exists between the substrates 101.

Description

  The present invention relates to a substrate cleaning method and a substrate cleaning apparatus for cleaning a semiconductor substrate such as a silicon substrate for solar cells and a thin plate substrate such as a glass substrate for liquid crystal.

  In the manufacturing process of a solar cell using crystalline silicon, various wet treatments are performed in which treatment is performed by immersing a substrate in a chemical solution. For example, first, an etching cleaning process using an alkali solution or an acid solution is performed to form a texture for the purpose of light confinement on a silicon substrate. Subsequently, after the impurity diffusion for forming the pn junction, an impurity glass layer is formed on the substrate surface as a subsidiary, and thus an etching cleaning process using a hydrofluoric acid solution is performed to remove the impurity glass layer. In order to improve the performance of solar cells, passivation is performed with a dielectric film that reduces the dangling bonds of silicon, which is a defect on the outermost surface of the substrate. To improve the passivation effect, a combination of acids and alkalis is used. It is necessary to improve the cleanliness of the silicon substrate surface as much as possible by cleaning.

  Such substrate cleaning is generally performed by sequentially immersing a plurality of wafers stored in a carrier cassette in units of carrier cassettes in a wet bench type cleaning tank in which a plurality of cleaning tanks are continuously arranged. This method is called batch wet cleaning, and the configuration of the apparatus is disclosed in, for example, Japanese Patent Laid-Open No. 6-163506 (Patent Document 1).

  By the way, there is a problem that the power generated by the current solar cell is still higher in power generation cost than conventional commercial power, and therefore, a significant reduction in manufacturing cost is required. In particular, in the mainstream crystalline silicon solar cells, the cost reduction is progressing by thinning the substrate, and the thickness of the substrate is currently 180 μm to 250 μm, but it is necessary to realize 50 μm to 150 μm in the future. It is said.

  However, when the substrate is thinned as described above, in the conventional batch-type wet cleaning, when the carrier cassette is picked up from the cleaning liquid, a phenomenon in which adjacent substrates are stuck in the carrier cassette often occurs. This phenomenon is caused by the attractive force acting between the substrates due to the surface tension of the cleaning liquid and the elastic deformation caused by the reduction in the rigidity of the substrate accompanying the thinning of the substrate.

  And, as a matter of course, the substrate adhered in this way is not normally washed and dried, and becomes defective as it is, so that the productivity is remarkably lowered.

  In addition, as a simple workaround for this problem, there is a method of widening the storage interval of the substrates, but the number of processed sheets per batch is reduced, and a new mold is added every time the thickness of the substrate is changed. Since it was necessary to prepare, there was a problem that the cost became high.

JP-A-6-163506

  The present invention has been made in view of the above-described problems in the prior art, and provides a substrate cleaning method and a substrate cleaning apparatus that prevent sticking between substrates after cleaning without reducing productivity. Objective.

The present invention provides the following substrate cleaning method and substrate cleaning apparatus as means for solving the above problems.
[Claim 1]
A step of immersing a plurality of substrates held and stored in a carrier cassette in a state spaced apart from each other by a predetermined interval in a cleaning liquid in a cleaning tank, and cleaning the substrates, and mixing bubbles in the cleaning liquid between the substrates And a step of pulling up the carrier cassette and taking out the substrate from the cleaning liquid in a state where a bubble-containing cleaning liquid exists between the substrates.
[Claim 2]
The substrate cleaning method according to claim 1, wherein the substrate is a silicon substrate having a thickness of 50 to 250 μm for manufacturing a solar cell.
[Claim 3]
3. The substrate cleaning method according to claim 1, wherein the substrates are arranged in the carrier cassette in a state of being separated from each other at an interval of 1 to 8 mm.
[Claim 4]
The substrate cleaning method according to claim 1, wherein the cleaning liquid has a surface tension of 20 mN / m or more and 76 mN / m or less.
[Claim 5]
The substrate cleaning method according to claim 1, wherein a density of bubbles in the bubble-containing cleaning liquid is 50 / ml or more.
[Claim 6]
A cleaning tank that stores cleaning liquid, a carrier cassette that holds and stores a plurality of substrates spaced apart from each other at a predetermined interval, carrier transport means that allows the carrier cassette to enter and exit the cleaning tank, and the carrier cassette that is a cleaning tank A bubble supply means for causing bubbles to be mixed in the cleaning liquid between the substrates immersed in the cleaning liquid by being carried in,
The substrate is immersed in a cleaning solution for cleaning, bubbles are mixed in the cleaning solution between the substrates, and the carrier cassette is lifted from the cleaning tank in a state where the bubble-containing cleaning solution exists between the substrates, and the substrate is removed. A substrate cleaning apparatus that performs control to remove from a cleaning liquid.

  According to the substrate cleaning method and the substrate cleaning apparatus of the present invention, air bubbles are mixed in the cleaning liquid between the substrates immersed in the cleaning liquid, and the carrier cassette is pulled up in a state where the bubble-containing cleaning liquid exists between the substrates. By removing from the cleaning liquid, the bubble-containing cleaning liquid increases the area of the gas-liquid interface between the substrates and suppresses sticking between the substrates to prevent poor cleaning, so the thin substrate can be cleaned using a conventional carrier cassette. It becomes possible to carry out stably. In addition, it is possible to reduce costs and improve productivity in solar cell applications.

It is a section schematic diagram showing the example of composition (1) of the substrate cleaning device concerning the present invention. It is a top view which shows the structure of a carrier cassette. It is a section schematic diagram showing the example of composition (2) of the substrate cleaning device concerning the present invention. It is a section schematic diagram showing the example of composition (3) of the substrate cleaning device concerning the present invention. It is a section schematic diagram showing the example of composition (4) of the substrate cleaning device concerning the present invention.

Hereinafter, a configuration of a substrate cleaning method and a substrate cleaning apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing a configuration example (1) of a substrate cleaning apparatus according to the present invention.
The substrate cleaning apparatus according to the configuration example (1) of the present invention includes a carrier cassette 102 in which a plurality of substrates 101 are housed at predetermined intervals, a cleaning tank 105 containing a cleaning liquid 104, and a cleaning of the carrier cassette 102. A carrier transporter 103 that is a carrier transport unit that performs immersion in the tank 105 and removal from the cleaning tank 105.

  In the figure, reference numeral 107 denotes a bubble generating / supplying device. The bubble generating / supplying device 107 is connected to a gas supply pipe 108 having a valve 109 and a cleaning liquid circulation pipe 110 having a pump 111 interposed therebetween. In addition, a bubble mixed cleaning liquid supply pipe 107 a is further connected to the bubble generation supply unit 107. Further, the tip of the bubble mixed cleaning liquid supply pipe 107a communicates with a bubble introduction recess 106 formed at the bottom position of the cleaning tank facing the plurality of substrates 101 when the carrier cassette 102 is carried into the cleaning tank 105. Yes.

  In the substrate cleaning apparatus having such a configuration, the cleaning liquid 104 in the cleaning tank 105 is introduced from the cleaning liquid circulation pipe 110 and the gas is introduced from the gas supply pipe 108 to the bubble generating / supplying unit 107, and the bubble-containing cleaning liquid is contained therein. Then, this is supplied from the bubble mixed cleaning liquid supply pipe 107 a to the bubble introduction recess 106, and this bubble mixed cleaning liquid is introduced between the substrates 101.

  Here, the substrate 101 is a material to be cleaned which is cleaned by the substrate cleaning apparatus of the present invention, and is, for example, a semiconductor substrate such as a crystalline silicon substrate used for manufacturing a solar cell or a thin substrate such as a glass substrate for liquid crystal. . In this case, the thickness of the substrate 101, in particular, the thickness of the silicon substrate for manufacturing the solar cell is preferably 50 to 250 μm, and the substrates 101 are arranged so as to be spaced apart at an interval of 1 to 8 mm. preferable.

  The substrate 101 has a thickness in consideration of productivity, rigidity, and the like. For example, the surface tension of the cleaning liquid 104 at room temperature is 20 mN / m or more and 76 mN / m or less, and the cleaning liquid 104 in the cleaning tank 105 is used. In the case where the density of the bubbles is 50 / ml or more, the effect of the present invention is more advantageously obtained in the range of 50 μm or more and 250 μm or less. If the thickness is less than 50 μm, the rigidity of the substrate 101 is lowered and it is difficult to hold the substrate 101 with a carrier cassette. If it exceeds 250 μm, the rigidity of the substrate 101 is sufficiently high and sticking hardly occurs, so that it is not necessary to introduce bubbles.

  In addition, if the distance between the substrates 101 is less than 1 mm, it may be difficult to prevent the substrates 101 from sticking even by supplying the bubble-containing cleaning liquid. If the distance between the substrates 101 is more than 8 mm, the number of the substrates 101 that can be stored in the carrier cassette 102 is small. This may reduce the efficiency (productivity) of the cleaning process.

  The carrier cassette 102 is mainly formed of a synthetic resin, and holds a plurality of substrates 101 at regular intervals so that the substrates 101 can be cleaned while being separated from each other.

FIG. 2 shows a specific example of the carrier cassette 102.
The carrier cassette 102 is conventionally used for substrate cleaning, and has a pair of frames 102b and 102b that are plate-shaped and arranged to face each other, and a predetermined interval is provided between the frames 102b and 102b. The box-shaped case member having the frames 102a and 102a for connecting both ends of the pair of frames 102b and 102b as described above, and at least one direction of the box shape, for example, the vertical direction when immersed in the cleaning tank 105 (see FIG. In FIG. 2, the liquid is opened in a direction perpendicular to the paper surface). A plurality of partitions 102c are erected at equal intervals in the direction perpendicular to the liquid passing direction in the carrier cassette 102 in a state of being opposed to each other on the inner surfaces of the frames 102b and 102b. Thus, both end portions of one substrate 101 are inserted between the partitions 102c adjacent to each other, and a predetermined number of substrates 101 are held in the carrier cassette 102 in a state where a gap is secured between the substrates 101. Become.

  In addition, although the width w and the installation space | interval p of the partition 102c are not specifically limited, From a viewpoint of the productivity of a solar cell, it is preferable to set it as w = 2-3mm and p = 4-6mm, respectively. That is, if w = 2 mm or less and p = 4 mm or less, it may be difficult to hold the substrates 101 without contacting each other, and if w = 3 mm or more and p = 6 mm or more, the substrate 101 that can be held by one carrier cassette 102. There is a risk that the number of sheets will be reduced and the productivity will deteriorate.

  As shown in FIG. 1, the carrier transporter 103 immerses the carrier cassette 102 in the cleaning liquid 104 in the cleaning tank 105 by gripping and suspending both sides of the carrier cassette 102 above the cleaning tank 105, The carrier cassette 102 is taken out from the cleaning tank 105 by lifting. The drive mechanism of the carrier conveyance machine 103 may be a known one.

  The cleaning liquid 104 is selected according to the purpose of cleaning the substrate 101. For example, as the cleaning liquid used in the solar cell manufacturing process, various liquids such as organic solvents and acidic and alkaline solutions are used according to each processing process.

That is, in the solar cell manufacturing process, there is a texture forming process in which a texture for light confinement is first formed on the substrate surface. In this process, a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution or a hydroxide is generally used as a cleaning liquid. An alkali cleaning solution such as tetramethylammonium aqueous solution or an acid cleaning solution in which acetic acid or water is mixed with hydrofluoric acid is used.
In addition, after the impurity diffusion treatment for forming the pn junction is subsequently performed, an impurity glass layer is formed on the substrate surface as a secondary, so that hydrofluoric acid is used as a cleaning liquid for etching cleaning for removing the impurity glass layer. Is used.
In addition, in order to improve the performance of solar cells, passivation is performed with a dielectric film that reduces silicon dangling bonds, which are defects on the outermost surface of the substrate. However, in order to enhance the passivation effect, the cleanliness of the silicon surface is minimized. Need to increase. For this purpose, an acid solution such as hydrogen peroxide, nitric acid, hydrofluoric acid, sulfuric acid or hydrochloric acid, or an alkaline solution such as aqueous ammonia or tetramethylammonium solution is used in combination as the cleaning liquid.
Further, when patterning a diffusion layer, an insulating film, or a metal film on a silicon substrate, masking is performed with an organic material such as an acid resist or a photoresist. For example, in a back electrode type solar cell in which the electrodes of the solar cell are formed only on the back surface opposite to the light receiving surface, since both the positive electrode and the negative electrode are formed on the back surface side, it is necessary to pattern the diffusion layers corresponding to both electrodes. For patterning the diffusion layer, a dielectric film such as a silicon oxide film or a silicon nitride film is used as a mask. For patterning these films, for example, an acid resist is used to expose the oxide film in a desired diffusion region, and then the mask is formed. The oxide film is removed with acid. After patterning of the oxide film, the acid resist is removed. Usually, an organic solvent such as acetone or methanol is used as a rough cleaning agent.

  It should be noted that a material suitable for the chemical cleaning liquid 104 as described above must be used for the cleaning tank 105, the bubble introduction recess 106, the bubble generation supply device 107, the cleaning liquid circulation pipe 110, and the portion of the pump 111 that contacts the cleaning liquid 104. is there. In most cases, various synthetic resins including vinyl chloride resin and fluororesin can be used.

  Here, the cleaning tank 105 stores the cleaning liquid 104 so that the carrier cassette 102 can be immersed therein.

  The bubble introduction recess 106 is a recess provided at the dipping position of the carrier cassette 102 at the bottom of the cleaning tank 105, and the bubble mixed cleaning liquid is supplied from the bubble generation supply unit 107 via the bubble mixed cleaning liquid supply pipe 107a. The bubble-containing cleaning solution is introduced between the substrates 101 in the carrier cassette 102 immersed in the cleaning tank 105. The size of the opening of the bubble introduction recess 106 at the bottom of the cleaning tank 105 is such that when the carrier cassette 102 is placed in the cleaning tank 105, the bottom of the carrier cassette 102 straddles the opening of the bubble introduction recess 106. It is preferable that both end portions of the bottom portion are supported by the bottom portion of the cleaning tank 105 and that the bottom portion of the carrier cassette 102 closes the opening of the bubble introduction recess 106 as much as possible. Thereby, the bubble mixed cleaning liquid in the bubble introduction recess 106 is efficiently supplied between the substrates 101 in the carrier cassette 102.

  A gas whose flow rate is adjusted by a valve 109 is supplied from a gas supply pipe 108 to a bubble generation supply unit 107, and a cleaning liquid 104 is supplied from a cleaning liquid circulation pipe 110 via a pump 111. The gas supplied in the vessel 107 and the cleaning liquid 104 are mixed to generate a cleaning liquid 104 containing bubbles of a predetermined size and density, and supplied to the bubble introduction recess 106.

  The bubble generation and supply device 107 is a means for generating a high-density and fine bubble-containing cleaning solution and supplying it to the cleaning tank 105 side (the bubble introduction recess 106 in this embodiment). As a method for generating such a bubble-containing cleaning liquid, any bubble generation method may be used as long as a desired bubble density is obtained. Examples thereof include a pressure dissolution method and a gas-liquid two-phase flow swirl method. In the present invention, commercially available bubble generators of these systems can be used.

  It should be noted that the bubble feeder with a strong water flow at the time of bubble supply may be damaged due to the vibration of the substrate 101 depending on the positional relationship between the bubble generation and supply device 107 and the carrier cassette 102 and the thickness of the substrate 101 in the substrate cleaning apparatus. Therefore, care must be taken such as increasing the distance between the bubble generating / supplying device 107 and the carrier cassette 102.

  The size and density of bubbles in the bubble mixed cleaning liquid introduced between the substrates 101 in the carrier cassette 102 are the thickness of the substrate 101, the partition width w of the carrier cassette 102 to be used, the partition installation interval p, the type of the cleaning liquid 104 (surface tension). ) Etc., the optimum conditions change greatly.

  Further, the attractive force generated between the substrates 101 by the cleaning liquid 104 is inversely proportional to the interface area between the bubbles supplied between the substrates 101 and the cleaning liquid 104. Accordingly, when the dimensions of the carrier cassette 102 and the surface tension of the cleaning liquid 104 are constant, and the substrate 101 is thinned, the substrate 101 is more easily elastically deformed. Therefore, the density of bubbles in the supplied bubble-containing cleaning liquid (supply bubble density) Need to be improved.

  For example, among cleaning liquids mainly used for cleaning silicon substrates for solar cells, organic solvents exhibit the lowest surface tension, and are usually used in a temperature range (15 to 25 ° C.) around room temperature (20 ° C.). It is approximately 20 to 40 mN / m (millinewton / meter). When the cleaning liquid 104 is such an organic solvent, the supply bubble density with respect to the substrate 101 having a thickness of more than 150 μm and not more than 250 μm is preferably at least 50 / ml to 150 / ml, more preferably 80 / ml to 120 / More preferred is ml or less. Further, the supply bubble density for the substrate 101 having a thickness of 50 μm or more and 150 μm or less under the same conditions is preferably 100 / ml or more and 350 / ml or less. At this time, when the supply bubble density is less than 50 / ml (when the substrate 101 is thicker than 150 μm and 250 μm or less) or less than 100 / ml (when the substrate 101 is 50 μm or more and 150 μm or less in thickness), the cleaning liquid 104 is used. In some cases, the effect of reducing the attractive force between the substrates 101 generated by the surface tension is small. When the supply bubble density exceeds 150 / ml (when the substrate 101 is thicker than 150 μm and 250 μm or less) or more than 350 / ml (when the substrate 101 has a thickness of 50 μm to 150 μm), the supply bubble density Even if it is further increased, the effect of reducing the attractive force between the substrates 101 generated by the surface tension of the cleaning liquid 104 may not change much.

  On the other hand, among cleaning liquids mainly used for cleaning silicon substrates for solar cells, water exhibits the highest surface tension, and is 58 to 76 mN / m in a normal use temperature range (15 to 100 ° C.). When the cleaning liquid 104 is such water, the supply bubble density with respect to the substrate 101 having a thickness of more than 150 μm and not more than 250 μm is preferably 1000 / ml to 4000 / ml, more preferably 2000 / ml to 3000 / ml. Is more preferable. In addition, the supply bubble density for the substrate 101 having a thickness of 50 μm or more and 150 μm or less under the same conditions is preferably 4000 / ml or more and 30000 / ml or less. At this time, when the supply bubble density is less than 1000 / ml (when the substrate 101 is thicker than 150 μm and 250 μm or less) and less than 4000 / ml (when the substrate 101 is 50 μm or more and 150 μm or less in thickness), the cleaning liquid 104 is used. In some cases, the effect of reducing the attractive force between the substrates 101 generated by the surface tension is small. When the supply bubble density exceeds 4000 / ml (when the substrate 101 is thicker than 150 μm and 250 μm or less) or more than 30000 / ml (when the substrate 101 has a thickness of 50 μm or more and 150 μm or less), the supply bubble density Even if it is further increased, the effect of reducing the attractive force between the substrates 101 generated by the surface tension of the cleaning liquid 104 may not change much.

  Moreover, there is no restriction | limiting in the kind of gas used in order to form a bubble in the washing | cleaning liquid 104, You may use air | atmosphere (air). In addition, when high cleanliness is required or when chemical reactions with the surface of the substrate 101 are disliked, it is preferable to use an inert gas such as pure argon or nitrogen.

Substrate cleaning using the substrate cleaning apparatus of the present invention is performed in the following procedure (see FIG. 1).
(Procedure 1) The carrier cassette 102 in which the substrate 101 is stored is immersed in the cleaning liquid 104 in the cleaning tank 105 by the carrier transporter 103. At this time, the substrate 101 accommodated in the carrier cassette 102 is disposed so as to straddle the bubble introduction recess 106 at the bottom of the cleaning tank 105.
(Procedure 2) The substrate 101 is cleaned. The substrate 101 may be cleaned by a known process.
(Procedure 3) When the cleaning process of the substrate 101 is completed, supply of the gas and the cleaning liquid 104 to the bubble generation supply unit 107 is started. Thereby, the bubble generation supply unit 107 generates a bubble mixed cleaning liquid and supplies it to the bubble introduction recess 106.
(Procedure 4) The supply of the gas and the cleaning liquid 104 to the bubble generation supply device 107 is continued until the carrier cassette 102 is completely taken out. As a result, the bubble mixed cleaning liquid is continuously supplied from the bubble generation supply unit 107 to the bubble introducing recess 106 at a constant pressure, and the bubble mixed cleaning liquid is supplied between the substrates 101 in the carrier cassette 102 from the bubble introducing recess 106.
(Procedure 5) The bubble-containing cleaning liquid that has entered the carrier cassette 102 flows upward between the substrates 101 in the carrier cassette 102. At this time, the presence of bubbles in the cleaning liquid between the substrates 101 increases the area of the gas-liquid interface, and the attractive force due to the surface tension of the cleaning liquid 104 applied to the substrate 101 is greatly reduced. As a result, the adjacent substrates 101 are not attached to each other and the distance between them is maintained.
(Procedure 6) Next, the carrier cassette 102 is taken out from the washing tank 105 by the carrier transporter 103. At this time, the adjacent substrates 101 in the carrier cassette 102 are not attached to each other and are taken out from the cleaning liquid surface in a state in which the distance between the two is maintained, so that a cleaning failure caused by the attachment of the substrates 101 is prevented. be able to.

  Note that the timing of supplying bubbles in the substrate cleaning using the substrate cleaning apparatus of the present invention is not particularly limited, but it is necessary that the bubbles are sufficiently supplied between the substrates 101 before the substrate 101 passes through the cleaning liquid surface. Therefore, the bubble-containing cleaning liquid is introduced into the carrier cassette 102 at least before the carrier cassette 102 starts to rise for removal from the cleaning tank 105 (before the procedure 6). Alternatively, regardless of the conveyance timing of the carrier cassette 102, the bubble supply may be performed continuously throughout the cleaning process.

  Further, the configuration of the bubble supply means is not limited to the configuration shown in FIG. 1 as long as the bubble mixed cleaning liquid is introduced into the carrier cassette 102. For example, as shown in FIG. 3, without providing the bubble introduction recess 106 at the bottom of the cleaning tank 105 ′, the bubble-containing cleaning liquid is supplied from the bubble generation supply unit 107 via the bubble-containing cleaning liquid supply pipe 107a to the cleaning tank 105 ′. The bubble-containing cleaning liquid may be introduced into the carrier cassette 102 by being supplied directly to the vicinity of the bottom. In this case, the bubble generation supply unit 107 (including the bubble mixed cleaning liquid supply pipe 107a, the gas supply pipe 108, the valve 109, the cleaning liquid circulation pipe 110, and the pump 111) serves as the bubble supply means. 3 that are the same as those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1 and description thereof is omitted (the same applies to FIGS. 4 and 5).

  Further, it is not always necessary to circulate the cleaning liquid 104. For example, as shown in FIG. 4, a cleaning liquid supplier 112 for storing the cleaning liquid 104 is provided, and a bubble mixed cleaning liquid is generated from the cleaning liquid supplier 112 to the bubble generation supply 107. Alternatively, the cleaning liquid 104 may be supplied, and the cleaning liquid 104 may be overflowed from the cleaning tank 105 ″ and discharged as it is.

  Further, as shown in FIG. 5, the bubble generating / supplying device 107 ′ is disposed in the bubble introduction recess 106 ′ below the cleaning tank 105, and the cleaning liquid and the gas are mixed in the bubble introduction recess 106 ′. It may be configured to generate. Alternatively, it is assumed that the gas generating / supplying device 107 ′ is made of a porous material in which a large number of micropores are formed, and the cleaning liquid is not supplied to the bubble generating / supplying device 107 ′, but only the gas is supplied and the bubble generating / supplying device 107 ′ A configuration may be adopted in which gas is discharged from the fine holes to generate fine bubbles in the bubble introduction recess 106 '.

Examples of the present invention will be described below.
[Example 1]
The substrate was cleaned under the following conditions.
(Substrate cleaning process)
(1) Substrate used / substrate 101; silicon substrate for solar cell (15 cm square, 150 μm thick)
(2) Substrate cleaning device (shown in FIG. 1)
Carrier cassette 102; partition width w = 2 mm, partition installation interval p = 4 mm
Washing liquid 104: industrial methanol (surface tension (20 ° C.): 22.11 mN / m)
・ Cleaning tank 105: Quartz cleaning tank (volume: 80L)
・ Bubble generation and supply device 107; pressure dissolution method, gas used: Ar)
(3) Substrate cleaning procedure (i) 50 substrates of 90 μm thickness are stored in the carrier cassette 102, and the carrier cassette 102 is immersed in industrial methanol as the cleaning liquid 104 in the cleaning tank 105 by the carrier transporter 103, The substrate 101 was held for a sufficient cleaning time.
(Ii) Next, the pump 111 is activated to supply the cleaning liquid 104 to the bubble generation supply unit 107, and the valve 109 is adjusted to supply a predetermined flow rate of Ar gas to generate a bubble-containing cleaning liquid. The bubble mixed cleaning liquid was supplied into the carrier cassette 102 via the bubble introduction recess 106. The bubble density of the bubble-containing cleaning liquid in the bubble introduction recess 106 at this time was measured with a laser light blocking type particle counter.
(Iii) When the bubbles were sufficiently supplied between the substrates 101, the carrier cassette 102 was taken out of the cleaning tank 105 by the carrier transfer device 103 while continuing to supply the bubble-containing cleaning liquid.

(Evaluation)
By changing the conditions of the bubble generation and supply device 107, the bubble density of the bubble mixed cleaning liquid in step S22 is changed to 0 / ml (no bubbles) and 80 / ml, and the substrate cleaning process is performed for each bubble density. After the removal, the substrate 101 is taken out from the carrier cassette 102. If the surface of the substrate 101 is visually recognized as dirty, the substrate 101 is determined to be defective, and the substrate 101 is not defective. The defective rate (number of defective samples / 50) was examined.
In addition, the same experiment was performed 3 times for each bubble density of the bubble-containing cleaning solution, and the average value of the defective rate was obtained.
The results are shown in Table 1.

[Example 2]
In Example 1, the thickness of the substrate 101 (solar cell silicon substrate) is set to 90 μm, and the conditions of the bubble generation and supply device 107 are changed, whereby the bubble density of the bubble-containing cleaning liquid in step S22 is 0 / ml (bubbles). The substrate cleaning process was performed under the same conditions as in Example 1 except that, and the defect rate due to the sticking between the substrates 101 was examined in the same manner.
The results are shown in Table 2.

  Although the present invention has been described with the embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and other embodiments, additions, modifications, deletions, etc. Can be changed within the range that can be conceived, and any embodiment is included in the scope of the present invention as long as the effects and advantages of the present invention are exhibited.

101 Substrate 102 Carrier cassette 102a, 102b Frame 102c Partition 103 Carrier transporter 104 Cleaning liquid 105, 105 ′, 105 ″ Cleaning tank 106, 106 ′ Bubble introducing recess 107, 107 ′ Bubble generation supply 107a Bubble mixed cleaning liquid supply pipe 108 Gas Supply pipe 109 Valve 110 Cleaning liquid circulation pipe 111 Pump 112 Cleaning liquid supplier w Partition width p Partition setting interval

Claims (6)

  A step of immersing a plurality of substrates held and stored in a carrier cassette in a state spaced apart from each other by a predetermined interval in a cleaning liquid in a cleaning tank, and cleaning the substrates, and mixing bubbles in the cleaning liquid between the substrates And a step of pulling up the carrier cassette and taking out the substrate from the cleaning liquid in a state where a bubble-containing cleaning liquid exists between the substrates.   The substrate cleaning method according to claim 1, wherein the substrate is a silicon substrate having a thickness of 50 to 250 μm for manufacturing a solar cell.   3. The substrate cleaning method according to claim 1, wherein the substrates are arranged in the carrier cassette in a state of being separated from each other at an interval of 1 to 8 mm.   The substrate cleaning method according to claim 1, wherein the cleaning liquid has a surface tension of 20 mN / m or more and 76 mN / m or less.   The substrate cleaning method according to claim 1, wherein a density of bubbles in the bubble-containing cleaning liquid is 50 / ml or more. A cleaning tank that stores cleaning liquid, a carrier cassette that holds and stores a plurality of substrates spaced apart from each other at a predetermined interval, carrier transport means that allows the carrier cassette to enter and exit the cleaning tank, and the carrier cassette that is a cleaning tank A bubble supply means for causing bubbles to be mixed in the cleaning liquid between the substrates immersed in the cleaning liquid by being carried in,
The substrate is immersed in a cleaning solution for cleaning, bubbles are mixed in the cleaning solution between the substrates, and the carrier cassette is lifted from the cleaning tank in a state where the bubble-containing cleaning solution exists between the substrates, and the substrate is removed. A substrate cleaning apparatus that performs control to remove from a cleaning liquid.

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